Neurotransmitters transporters are located in presynaptic specializations. They inactivate neurotransmitter-mediated neurotransmission following exocytotic release by a simple reuptake mechanism. Recent crystallographic examination of bacterial homologs to mammalian neurotransmitter transporters provides a structural scaffold which supports transport by an alternative access mechanism. Monoamine transporters are a target of clinically relevant drugs: (i) antidepressants competitively block the reuptake of monoamines. Thereby, these compounds enhance the extracellular monoamine concentration which is relevant for clinical success. (ii) amphetamines and cathinones, which behave as substrates of the transporters, trigger non-exocytotic neurotransmitter release (efflux). The exact molecular mechanism of the psychostimulant action, however, still remains enigmatic.

Techniques:

We use biochemical and fluorescence spectroscopical methods for the determination of the neurotransmitter transporter function. These include radioactively labeled tracer flux measurements (uptake/efflux experiments), flux measurements of fluorescent tracer and electrophysiological experiments (patch-clamp measurements in the whole cell configuration and two-electrode voltage clamp measurements). We work both with heterologously expressed transporters in cell lines (with/without mutagenesis to examine the structure/function relationship and concomitant quantitative structure activity relationship, QSAR) and native brain tissue (ex vivo) as well as primary neuronal cell culture. We explore the conformational equilibrium and the quaternary structure of transporters and interacting proteins by fluorescence resonance energy transfer (FRET) microscopy. Furthermore, we examine our psychostimulant drugs also in in vivo in behavioral-pharmacological experiments. We also employ computational approaches (QSAR), molecular modeling and molecular dynamics simulations.